A transformer was one of the critical components needed to make an electrical power system based on alternating current. Transformers raise and lower the electrical voltage (or potential) or the current, depending on the design. Electrical inventors Lucien Gaulard and John Gibbs introduced a practical design in Europe in 1882. George Westinghouse licensed their design and William Stanley, an engineer working in his company, added refinements that improved the device. This potential transformer has two coils of wire–one coil with a few turns of thick wire, the other with many turns of thin wire. A current passing through one (the primary coil) induces a current in the other (the secondary coil). The voltage can be raised or lowered depending on which coil serves as primary.
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